Abstract:

Positive emotion plays an important role in the improvement of clinical symptoms and the recovery of social function in patients with depression. In recent years, the development of neurofeedback technology provides an effective approach to enhance the positive emotion of depression. The traditional treatments that target the positive affect are subjective, have a relatively limited impact and lack of objective outcome measures. In contrast, neurofeedback technology based on objective physiological and image indicators has important clinical application value in enhancing positive emotions in depression. Neurofeedback, as a non-invasive technology, uses various electrophysiological methods and neuroimaging technologies to obtain real-time measurements of brain activity and provide feedback signals to subjects, so that the subjects can learn self-control over the activity in a brain area related to emotions through certain strategies. Crucially, it can evaluate objectively and quantitatively the improvement of positive emotions as well as provide more targeted treatments. However, the existing studies have great heterogeneity in experimental paradigms, parameter settings and individual efficacy, especially in the early studies of electroencephalographic (EEG)-neurofeedback training. Adding memory specificity training to the experimental paradigm can more effectively induce positive emotions in patients with depression. Other effectiveness of positive emotion-inducing strategies that may be combined with neurofeedback can be explored, such as psychological intervention that target the positive valence systems (PVS) to increase positive emotions. In this review, training protocols, the influencing factors of the protocols of neurofeedback and target brain regions of neurofeedback training based on imaging biomarkers will be discussed and summarized.EEG and functional magnetic resonance imaging (fMRI) are two neuroimaging modalities used for emotion regulation neurofeedback. EEG frontal asymmetry was used in several previous studies for emotion regulation using the power spectrum of frontal EEG channels in the special frequency band(frontal alpha EEG asymmetry). For positive emotion regulation based on fMRI neurofeedback is based on (blood oxygenation level-dependent,BOLD) activity of target affective brain region, as well as two regions’ fMRI functional connectivity or effective connectivity. Due to the fundamental role of the amygdala in the emotional processing of depression makes it a "star brain region" for the intervention of positive emotion deficit in patients with depression. Targeting brain circuits and complex brain networks engaged in the regulation of positive emotions have more powerful application value in the treatment of depression. Clinical populations may benefit from multivariate pattern neurofeedback training.The importance of neurofeedback experiment design and results reporting standards is emphasized, and the validity, feasibility, portability and extensibility of research design should be considered in neurofeedback protocols applied to neurological and psychiatric disorders. The feasibility of turning fMRI neurofeedback into a widely available clinical intervention is questionable. In contrast, functional near-infrared spectroscopy (fNIRS) is a relatively inexpensive and portable brain imaging technique that can be easily implemented at any location and has more potential for widespread clinical implementation than fMRI neurofeedback. Despite neurofeedback has already been used successfully to change brain responses in depressive patients, some participants never learn to control their brain responses at all. These participants are often referred to in the neurofeedback literature as non-responders. Unfortunately, few studies have focused on the proportion of non-responders. Given the not negligible proportion of non-responders, there is a strong need to understand the inter-individual differences in neurofeedback performance. Analysis of individual differences in neurofeedback training sheds light on successful self-regulation of the affective brain. Those who fail to successfully regulate may be associated with abnormal reward processing. A potential treatment target based on reward circuits and optimization schemes of neurofeedback will be recommended. It is expected to provide an operable reference scheme for positive emotion recovery in clinical depression. It lays a foundation for the clinical translation and popularization of neurofeedback technology in the treatment of clinical symptoms and social function rehabilitation of depression in the future.

Key words: positive affect, neurofeedback, depression, anhedonia, electroencephalography, functional magnetic resonance imaging